Measurement of isomeric yield ratios of Y-86m,Y-g, Y-87m,Y-g, and Zr-89m,Zr-g in the photonuclear reactions of Y-89 and Zr-nat at the end-point bremsstrahlung energies of 45 and 55 MeV

Abstract

The isomeric yield ratios of Y-88m,Y-g, Y-87m,Y-g, and Zr-89m,Zr-g produced in the reactions of Y-89 and Zr-nat with endpoint bremsstrahlung energies of 45 and 55 MeV have been determined by activation and off-line gamma-ray spectrometric technique using the 100 MeV electron linac at Pohang Accelerator Laboratory (PAL), Korea. The present data along with literature data show that the isomeric yield ratios of Y-86m,Y-g and Y-87m,Y-g in the Y-89(gamma,xn) and Zr-nat(gamma,x) reactions and those of Zr-89m,Zr-g in the Zr-nat(gamma,x) reaction increase with the endpoint bremsstrahlung energy, which indicates the effect of excitation energy. However, the increase trend of the isomeric yield ratios of Y-87m,Y-g in the (89)gamma(gamma,xn) reaction and Zr-89m,Zr-g in the Zr-nat(gamma,x) reaction are very fast from the threshold value to 30 MeV due to the giant dipole resonance effect. After certain point of excitation energy, the isomeric yield ratios increase slowly with the end-point bremsstrahlung energy due to the partition of energy in different reaction channels. It was also observed that in both the reactions, the isomeric yield ratios of (87m,g)gamma are always higher than those of Y-88m,Y-g. This is because of more number of particle emission and thus the disposition of more excitation energy needed for the formation of Y-86m,Y-g compared to Y-87m,Y-g. (C) 2014 Elsevier B.V. All rights reserved.